In U.S. Pat. No. 4,229,142, a pulse excited alternator has already been described comprising at least one coil surrounded by a magnetic circuit forming a gap with the magnetic ring of a piston moving between two positions, this gap having a length which varies as a function of the piston displacement. Ends of the coil are respectively connected to the positive and negative terminals of a constant voltage current source through two electronic gates controlled by a pulse device, unidirectional connections being moreover provided between each end of the coil and the opposite terminal of the current source.
The present invention relates to providing a magnetic coil which makes it possible to obtain a better ratio than previously between the power transferred upon each cycle and the mass of said magnetic ring.
For a given stroke of the magnetic ring upon its rectilinear displacement, the amount of power which is transferred is proportional to the mechanical forces exerted between the inductor and the mobile magnetic ring, and is particularly proportional to the component of these forces which is parallel to the direction of movement. This component, for a given front cross-section of magnetic material, is proportional to the magnetic field formed within the main gap which is no more than the volume swept by the displacement of the magnetic ring. Yet, it is necessary that such a magnetic field of a high magnitude be obtained by passage of the current in the coils without saturation of the ferromagnetic material circuit surrounding the coils and which localizes the useful fields in the main gap. These facts lead simultaneously to a saturation of the magnetic material of the ring without the fixed magnetic circuit of the inductor itself being saturated.
The present invention solves these problems, and permits also the reduction of the weight and the cost of a rectilinear generator of the type of that described in the above patent.
According to the invention, the generator comprises a mobile part made in the form of a magnetic ring constituted by ferromagnetic material sheets of a uniform thickness and width, and which are radially and regularly positioned.
According to another feature of the invention, the spacing between the sheets in the proximity of a residual gap formed between the magnetic ring and the opposite wall of the inductor is such that the proportion of ferromagnetic material of the magnetic ring in the area of the residual gaps represents 50 to 80% of the proportion of the sheets in the magnetic circuits of the inductor.
The invention relates also to a process for making the magnetic ring which is obtained by placing into a mold previously cut and bent sheets, the bent part of each sheet being placed in the mold symmetrically with respect to the bent part of the neighbouring sheets.
Various other features of the invention will moreover be revealed from the following detailed description.